The other morning a buddy and me were out checking cold barrel shots. On my 243 with an 8 twist barrel shooting 105 gr Berger vld's going 3050 fps he said it looked like a corkscrew through the spotting scope. We were either shooting 750 or 950 yards I don't remember which. Anyways the gun was on target so I had him shoot and I spotted and it sure did look like a corkscrew. All of our other guns would produce a normal vapor trail but this one sure does look funny. Anybody have a clue? Surely it's not unstable is it? I've taken this combo to 1400yrds before and it's accurate so I'm confused!!!!
Corkscrew vapor trail????
- Thread starter jabey9210
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SidecarFlip
Well-Known Member
My Pierce/Savage 308 did the same thing the other morning (at 200 yards on my private range), EXACTLY the same scenario only I was shooting and a friend was spotting. 165 Bergers jacked up a bit.
It has to do with a couple things, ambient temperature, dew point and relative humidity. I think the corkscrew vapor trail has to to with the barrel twist rate.
I could be wrong on all the above as it's the first time for me too.
You have to have the spotting scope almost directly in line with the flight path of the pill (or just slightly to the side) or it's not visible (we tried moving the spotting scope to a more oblique angle and the vapor trail vanished....
Didn't think much of it until you commented......
It has to do with a couple things, ambient temperature, dew point and relative humidity. I think the corkscrew vapor trail has to to with the barrel twist rate.
I could be wrong on all the above as it's the first time for me too.
You have to have the spotting scope almost directly in line with the flight path of the pill (or just slightly to the side) or it's not visible (we tried moving the spotting scope to a more oblique angle and the vapor trail vanished....
Didn't think much of it until you commented......
Laelkhunter
Well-Known Member
I was reading a post a while back about "Epicyclic Swerve". Bob McCoy wrote extensively about it in his book "Modern External Ballistics".
I won't even try to explain it in detail, but it has something to do with the bullet not stabilizing until further downrange, and it (the bullet) tends to travel in a corkscrew pattern until it does stabilize.
I had never heard of it before, but Mr. McCoy has a vast better knowledge on the info than I ever do.
Could this explain what you saw?
I won't even try to explain it in detail, but it has something to do with the bullet not stabilizing until further downrange, and it (the bullet) tends to travel in a corkscrew pattern until it does stabilize.
I had never heard of it before, but Mr. McCoy has a vast better knowledge on the info than I ever do.
Could this explain what you saw?
Maybe but this combo has never given any indication of being unstable. It'll produce .5 groups at 100 and this is the first time the corkscrew vapor trail has been noticed. I would hope that if it needed time to settle that 950 yards would be plenty but it would corkscrew the entire time until it hit the 12" x12" plate!!!
Sully2
Well-Known Member
Its just the vortex created when any HI SPEED projectile goes theu the air...whether it be a car...a bullet...or whatever. Even an airplane wingtip
Schnyd112
Well-Known Member
+1, conditions have to be just right to see it but it happens every time. There is a video out there of a guy shooting at desert bighorn sheep and you can see it 4 times in a row. Pretty neat to watch the bullet "screw" into the target.
It wouldn't have concerned me if the other guns we were shooting were doing it, but there was also a 7wsm, 280, 260 and a 223. With the spotting scope in the same place and shooting from the same place you could see vapor trails of all the guns but the .243 was the only one that appeared to have a corkscrew pattern at both 750yrds and 950yrds!!!
Laelkhunter
Well-Known Member
I wouldn't worry about it if you can hit a 12" X 12" plate at 950 yards. The rifle and ammo sounds pretty accurate, and I would say- No need to worry. Enjoy your successful endeavor at long range shooting !!
Remember that the trace you see is not the actual bullet, but the disturbance left in the air from the bullet. As such, the trace is carried by the air/wind in whatever direction it's blowing.
In other words, if you're shooting thru a swirl or eddie in the wind, the bullet may not be deflected enough to see or notice, but the trace you're seeing is.
Epicyclic swerve is a real thing, but happens to a much smaller magnitude than most realize. The swerve radius is typically 10% of the caliber or less, so like 0.030" for a .30 caliber bullet. Not enough to see. Epicyclic swerve can happen for bullets that are fully stable. If their's a tip-off at the muzzle and the bullet has to settle down, that's where the very minor corkscrew flight path (epicyclic swerve) comes in. But again, it's not likely you were seeing this, but rather the trace blowing in the wind.
-Bryan
In other words, if you're shooting thru a swirl or eddie in the wind, the bullet may not be deflected enough to see or notice, but the trace you're seeing is.
Epicyclic swerve is a real thing, but happens to a much smaller magnitude than most realize. The swerve radius is typically 10% of the caliber or less, so like 0.030" for a .30 caliber bullet. Not enough to see. Epicyclic swerve can happen for bullets that are fully stable. If their's a tip-off at the muzzle and the bullet has to settle down, that's where the very minor corkscrew flight path (epicyclic swerve) comes in. But again, it's not likely you were seeing this, but rather the trace blowing in the wind.
-Bryan
If I had only been shooting this gun I wouldn't have given it a second thought because I was on target at 950yrds. I would have just wrote it off to current atmospheric conditions. I was only perplexed by the fact that only this particular bullet was producing such a funky vapour trail and the rest weren't. We would alternate between guns and every time I got back to the .243 it would have the corkscrew vapor trail!!!
Lone Hunter
Well-Known Member
I've had it happen with .22 cal bullets and 175 SMK's also Bergers. Looks weird but I was hitting the target so no concern to me. Looked cool to watch though. It's humid where I shoot most of the time so I figured that had something to do with it.
adam32
Well-Known Member
It's the best bullet you were shooting too...so maybe it was just saying "screw you" to the rest of the bullets...
gun)
gohring3006
Well-Known Member
If you entered the BC that Berger list and hit at 950. Then it had no influence on the bullet.
Its just the way it leaves a trail.
Its just the way it leaves a trail.
